Electrophoresis, generally, relates to the separation of a complex substance into its component fractions by procedures based upon the migration or mobility of electrically charged fractions in a direct current electric field. With an electric field developed between two spaced electrodes and a substance placed therein, the variously charged components or constituents of the substance move or migrate toward the respective electrodes of opposite charge and the respective components or constituents will move with different mobilities, i.e., at different rates. Thus separation may be accomplished on the various component factions. This separation may take place on a suitable support medium such as an acrylamide gel saturated with an electrolyte. Each component separated by the electrophoresis procedure is subject to a qualitative and quantitative analysis and has therefore provided a useful tool in laboratory analysis of various substances such as albumen, enzymes, hemoglobin, carbohydrates, blood serum proteins, nucleic acids, etc.
Vertical gel electrophoresis refers to electrophoresis wherein the component fractions migrate under the influence of an electric field on a gel and in a vertical direction.
In the separation of short segments of DNA and RNA for the purpose of determining their nucleotide sequence, because the gel itself has pores of a specified size, these segments will be drawn through the pores at different speeds depending upon their size -- larger ones moving slower than smaller ones. This causes the segments to separate by size or length, which is the desired result both for sequencing and separation.
U.S. Pat. Nos. 3,932,265; 3,980,540; and 3,290,240 are generally representative of the available prior art for vertical gel electrophoresis apparatus.
Typically in commercially available units a comb is inserted into the gel prior to setting. When the gel sets the comb is removed forming slots into which samples are injected. The formation of the gel and slots is generally accomplished after the entire apparatus has been assembled.
A buffer or electrolyte chamber is typically disposed above the slots at the upper portion of the apparatus to insure fluid communication between the chamber and the samples. This arrangement sometimes requires additional structure to achieve cooling; see for example U.S. Pat. No. 3,616,457.
An important drawback in vertical gel electrophoresis is the apparatus typically comprises glass plates which form the walls of a mold into which the gel is placed. These plates have extending outer tabs at the top portion thereof. The upper electrolyte chamber is assembled about these tabs and secured with clamps and gaskets. Further, in some models actual introduction of the gel is accomplished in situ, that is after the entire apparatus has been assembled but prior to the introduction of the electrolyte.
Further gasketing material is used in the region where the tabs of the conventional plates extend into the buffer chamber to prevent leaking and also about the perimeter of the plates.
In setting up the vertical slab gel electrophoresis apparatus it has been found difficult to train personnel adept enough to quickly and efficiently assemble the units. The major problem is in the breaking off of the tabs of the plates in assembling a unit and the time required in properly assembling the unit with the attendant gaskets to prevent leaking.
The present invention overcomes the prior art problems by eliminating the need for tabbed plates used in the mold assembly, and physically separating the upper electrolyte chamber from the sample wells, eliminating the need for gaskets.